From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-18.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1E85BC64E69 for ; Mon, 23 Nov 2020 12:57:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D4A9520657 for ; Mon, 23 Nov 2020 12:57:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="dbMCncvy" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388014AbgKWM5E (ORCPT ); Mon, 23 Nov 2020 07:57:04 -0500 Received: from mail.kernel.org ([198.145.29.99]:35284 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387589AbgKWMue (ORCPT ); Mon, 23 Nov 2020 07:50:34 -0500 Received: from localhost (83-86-74-64.cable.dynamic.v4.ziggo.nl [83.86.74.64]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B67F8208C3; Mon, 23 Nov 2020 12:50:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1606135831; bh=Kpjv2vjdVuB+jkxDA0Kv2AL1fh/ayi1VCR2Z6onj4sw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=dbMCncvytmChhF1xDNVl/k/6VsAxQyYlaFi5Sg+r9SY2hZT0CKKjKsQK9W+Z1qe/8 HrC46RJQy5TI17/SH6AHm3txwV6mrus4NdTGBqGm4g95zPw/UBNwD5BZg+Qph4+gRd /Vs8q3Yk4NE0i0oN4nE5ncem+bTR6yoMvYec0/00= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , "Peter Zijlstra (Intel)" , Mel Gorman , Sasha Levin Subject: [PATCH 5.9 182/252] sched: Fix rq->nr_iowait ordering Date: Mon, 23 Nov 2020 13:22:12 +0100 Message-Id: <20201123121844.378746555@linuxfoundation.org> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201123121835.580259631@linuxfoundation.org> References: <20201123121835.580259631@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra [ Upstream commit ec618b84f6e15281cc3660664d34cd0dd2f2579e ] schedule() ttwu() deactivate_task(); if (p->on_rq && ...) // false atomic_dec(&task_rq(p)->nr_iowait); if (prev->in_iowait) atomic_inc(&rq->nr_iowait); Allows nr_iowait to be decremented before it gets incremented, resulting in more dodgy IO-wait numbers than usual. Note that because we can now do ttwu_queue_wakelist() before p->on_cpu==0, we lose the natural ordering and have to further delay the decrement. Fixes: c6e7bd7afaeb ("sched/core: Optimize ttwu() spinning on p->on_cpu") Reported-by: Tejun Heo Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mel Gorman Link: https://lkml.kernel.org/r/20201117093829.GD3121429@hirez.programming.kicks-ass.net Signed-off-by: Sasha Levin --- kernel/sched/core.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index b1e0da56abcac..c4da7e17b9061 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2505,7 +2505,12 @@ ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, #ifdef CONFIG_SMP if (wake_flags & WF_MIGRATED) en_flags |= ENQUEUE_MIGRATED; + else #endif + if (p->in_iowait) { + delayacct_blkio_end(p); + atomic_dec(&task_rq(p)->nr_iowait); + } activate_task(rq, p, en_flags); ttwu_do_wakeup(rq, p, wake_flags, rf); @@ -2892,11 +2897,6 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) goto unlock; - if (p->in_iowait) { - delayacct_blkio_end(p); - atomic_dec(&task_rq(p)->nr_iowait); - } - #ifdef CONFIG_SMP /* * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be @@ -2967,6 +2967,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) cpu = select_task_rq(p, p->wake_cpu, SD_BALANCE_WAKE, wake_flags); if (task_cpu(p) != cpu) { + if (p->in_iowait) { + delayacct_blkio_end(p); + atomic_dec(&task_rq(p)->nr_iowait); + } + wake_flags |= WF_MIGRATED; psi_ttwu_dequeue(p); set_task_cpu(p, cpu); -- 2.27.0